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斜拉桥中拉索承受着多种端部激励,可激发大幅空间振动.以斜拉索为对象,探究不同端部激励间相位差对其非线性振动的影响.首先,推导斜拉索无量纲离散控制方程,引入考虑相位的三向端部激励得到一般化模型;然后,针对拉索下端存在的纵桥向、竖向和横桥向激励的两两组合,受大幅或小幅激励,及其在主共振区或主参数共振区几组因素,共计12种工况,采用数值分析法分别研究了各工况下不同激励相位差时的斜拉索稳态响应.研究发现:激励相位差能加剧与激励频率相近的面内、外模态振动;在任意端部激励组合下,激励相位差不仅可使斜拉索非线性振动出现定量变化,还可改变内共振的表现形式.面内、外激励组合下,相位差对拉索响应幅值的影响以π为周期变化,且当相位差趋于π/2 + kπ (k = 0, 1, 2…)时影响最为突出;而面内激励组合下,以2π为变化周期,当相位差为π + 2kπ (k = 0, 1, 2, …)时其对稳态幅值的影响最显著.其原因是:面外激励关于拉索所在的竖直面对称,故其本质上以π为周期;而面内激励无此对称性,仍以2π为周期.因此,有无面外激励参与决定了激励间相位差对斜拉索响应的影响规律. 相似文献
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本文研究桥梁工程中含弯曲刚度斜拉索的面内面外内共振问题.描述了工程中斜拉索变形的三种状态,考虑弯曲刚度、大变形及垂度等因素,忽略斜拉索纵向惯性力的影响,运用Hamilton变分原理建立了含弯曲刚度的斜拉索面内面外耦合偏微分控制方程,采用Galerkin方法对偏微分方程离散,并运用多尺度摄动方法进行了求解,获得了斜拉索可能存在的内共振模式,以工程中一根斜拉索为例,运用有限元法对其进行动力特性分析,列出了斜拉索前10阶面内面外振动频率,找出面内面外可能产生内共振的模态,分别研究了主共振条件下斜拉索面内和面外1:1、2:1内共振情形,获得了有意义的结论. 相似文献
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研究了桥面侧振引起的斜拉索非线性振动问题。基于Hamilton原理建立了拉索的非线性振动控制方程,并利用多尺度法得到了斜拉索振动方程的二阶近似解。通过具体算例分析了斜拉索面内一阶模态与面外一阶模态相互耦合发生内共振的可能性,讨论了拉索倾斜角对拉索振动的影响,比较了在零初始条件和非零初始条件下拉索振动响应的区别。研究发现:拉索内共振发生在一定的激励频率和激励幅值区域内;改变倾斜角度,会影响拉索发生内共振时激励频率区域的大小;初始条件的不同,拉索的振动形式会相差很大。 相似文献
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应用拉索索端阻尼器是大跨度斜拉桥拉索减振的主要措施之一. 将主梁、索与阻尼器组合起来作为一个振动体系,通过理论分析与试验研究相结合的方法初步研究了主梁振动对拉索附加阻尼器减振效果的影响. 建立了由索、梁和Kelvin阻尼器组成的简化理论模型; 设计了索、梁和阻尼器组合系统的简化力学试验模型; 详细研究了主梁振动对拉索附加阻尼器减振效果的影响. 理论与试验分析结果表明: 对于容易发生索、梁耦合振动的拉索,主梁振动明显降低拉索附加阻尼器的减振效果;在大跨度斜拉桥拉索的减振设计中,需考虑主梁参与振动的影响. 相似文献
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为了提高斜拉索-磁流变阻尼器减振控制系统的稳定性, 提出了一种多指标约束的滑模非脆弱减振控制算法. 基于线性矩阵不等式(LMI), 利用H∞性能指标和保性能指标分别用来抑制外界扰动, 保证系统渐近稳定且具有一定上界指标, 并以区域极点配置表征减振控制稳定性与快速性, 方差表征小振幅和振动速度. 将非脆弱状态反馈控制与滑模控制相结合, 得到了多指标约束的滑模非脆弱减振控制算法设计形式及方法. 在强度为0.1002高斯白噪声随机扰动下, 对某跨海大桥C18、C13号斜拉索进行算例仿真. 结果表明, 该算法不仅使减振控制系统具有较优的保性能上界指标和较小的抗扰性能指标, 同时使拉索振动状态幅值降低91.11%~92.50%, 收敛时间缩短76.67%~84.00%. 相似文献
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Munetsugu KOTA Sae UEZONO Yusuke ISHIBASHI Sousuke KITAKAZE Hideki ARAKAWA 《Physical Therapy Research》2020,23(2):180
Objective: We focused on locomotive syndrome as a low physical function factor that may prevent patients with psychiatric disease from being discharged. The purpose of this study is to clarify the factors, including locomotive syndrome, that prevent discharge from psychiatric long-term care wards. Method: We enrolled 74 patients who were admitted to psychiatric long-term care wards at three different hospitals in Japan. Nurses or medical social workers in the ward were asked whether the planned discharge destination had been decided, and patients were categorized into a decided group and an undecided group. Outcome measures were age, sex, F code in the ICD-10 Classification of Mental and Behavioral Disorders, length of stay, chlorpromazine equivalent dose of antipsychotics, locomotive syndrome test scores (25-question GLFS, two-step test, stand-up test), and Barthel Index. Results: Based on the multivariate logistic regression analysis results, the length of stay and the two-step test score significantly explained the difference between the two groups. The odds ratio of a length of stay greater than 10 years was 8.42 times that of a length of stay less than 2 years (P=0.012, 95% CI=1.59, 44.53). Regarding the twostep test, the odds ratio for obtaining stage 2 was 10.62 times that for obtaining stage 0 (P=0.013, 95% CI=1.65, 68.23). Conclusion: Those who with longer length of stays and lower two-step test scores tended not to be decided the planned discharge destination. 相似文献
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As part of the modernisation of the UK National Health Service,specialist centres called treatment centres are being introducedthat cater solely for routine elective treatment for a relativelysmall number of conditions. In principle, such centres can adoptnew methods of operation, e.g. organising booked admissionson a cyclic basis, organised to make efficient use of treatmentresources. Assuming such a mode of operation, explicit cyclicformulae are derived for the mean and variance of bed demand.These take account of systematic differences between the lengthsof stay of different patient groups and also the effects ofemergency admissions. Using these formulae, optimisation methodsare discussed that have the potential for contributing to resourceplanning and to assist the process of booking patient admissions.Such optimisation methods can be used to help reduce overallcapacity needs or, conversely, to make better use of the capacityavailable. 相似文献